Pope Nicholas I to Constantinople’s envoy:
“Know, prince, that the vicars of Christ (the popes) are above the judgment of mortals, and that the most powerful sovereigns have no right to punish the crimes of popes, how enormous soever they may be….; for no matter how scandalous or criminal may be the debaucheries of the pontiffs, you should obey them, for they are seated on the chair of St. Peter.
“Fear, then, our wrath and the thunders of our vengeance, for Jesus Christ has appointed us with his own mouth absolute judges of all men, and kings themselves are submitted to our authority.”
(Source: A Complete History of the Popes of Rome, from Saint Peter, the First Bishop to Pius the Ninth, the Present Pope: Including the History of Saints Martyrs, Fathers of the Church, Religious Orders, Cardinals, Inquisitions, Schisms and the Great Reformers (Google eBook), by Louis Marie DeCormenin, James L. Gihon, 1857, p. 243.)